According to the World Health Organisation (WHO) a disease outbreak is the occurrence of cases of disease in excess of what would normally be expected in a defined community, geographical area or season.

An outbreak may occur in a restricted geographical area, or may extend over several countries.

It may last for a few days or weeks, or for several years. While animal disease outbreaks are not a new phenomenon, modern trends have dramatically increased the risks associated with them. In recent decades, rapid increases in human population and wealth have resulted in increased demand for livestock products meaning an unprecedented flow of both commodities and people across the world. Globalisation and increasingly international trade has enabled pathogens to spread as never before. In the last decade, disease outbreaks have led to the culling of hundreds of millions of animals and have incurred costs running into the hundreds of billions of dollars. Avian influenza viruses, to take just one example, are estimated to have led to the culling of 200 million birds in Asia alone, with losses of more than 10 billion US dollars for the region’s poultry sector. Efficient early warning and forecasting of disease trends through surveillance systems is key to effective containment and control of disease outbreaks. Early intervention such as the use of vaccines during a disease outbreak often leads to better outcomes with reduced disease burden and associated economic impact.


  • World Animal Health Information Database interface provides access to all data held within the OIE’s World Animal Health Information System (WAHIS): WAHID
  • WHO Global Alert and Response system: GAR
  • White paper: The Costs of Animal Disease
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